An aircraft wing box provides the structural core for an aircraft wing. The wing box includes a series of rib segments that are spaced apart longitudinally and connected to one or more wing spars and stringers extending the length of the wing box. The stringers are used to attach the wing skin or outer layer of the wing to the rib segments of the wing box. The stringers may structurally support the wing skin and transfer skin loads to the internal structure of the wing. In carbon fiber reinforced plastic (CFRP) stringer fabrication, each stringer may be made of multiple structural components, or members, that are cured and/or bonded together to form the stringer.
For example, a CFRP I-stringer 100, as shown in FIG. 1 is formed by curing two preformed C-shaped charge members 110, 120 together to form the web and portions of the upper flanges 112, 122 and lower flanges 114, 124 of the stringer 120. A top member 130 and a bottom member 140 are also cured to the upper flanges 112, 122 and lower flanges 114, 124 of the connected C-shaped charge members 110, 112 to create a top cap and bottom cap, respectively. A strip of material, such as called a noodle 150 is used between the top member 130 and C-shaped charge members 110, 120 and a bottom noodle 160 between the bottom member 140 and C-shaped charge members 110, 120, in order to fill in the applicable spaces. When all components are cured together, the CFRP I-stringer 100 is formed and ready for use.
One problem encountered with CFRP stringers is that they may be prone to delamination if excessive shear and moment forces are imparted on the stringer. Common locations for increased shear and moment forces on the stringer include locations where the ribs are bolted to the stringers. The delamination is likely to occur at a region around the noodles 150, 160 of the I-stringer 100. To decrease the likelihood of delamination, radius fillers are used at the locations where the ribs are bolted to the stringers. Radius fillers are conventionally configured as rectangular pieces of material that are sandwiched between the rib and stringer. They have an edge that is shaped to abut the junction of the vertical member 116 and the lower flange 114 of the C-shaped charge member 110, and to fill the radius 118 formed between the vertical member 116 and the lower flange 114 of the C-shaped charge member 110. In doing so, the radius fillers provide additional structural reinforcement to this joint and distribute the shear and moment forces in order to reduce the risk of delamination at the noodle region of the I-stringer 100.
One problem encountered with CFRP stringers is that they may be prone to delamination if excessive shear and moment forces are imparted on the stringer. Common locations for increased shear and moment forces on the stringer include locations where the ribs are bolted to the stringers. The delamination is likely to occur at the noodle region of the I-stringer. To decrease the likelihood of delamination, radius fillers are used at the locations where the ribs are bolted to the stringers. Radius fillers are conventionally configured as rectangular pieces of material that are sandwiched between the rib and stringer. They have an edge that is shaped to abut the junction 118 of the vertical member 116 and the lower flange 114 of the C-shaped charge member 110, and to fill the radius formed between the vertical member 116 and the lower flange 114 of the C-shaped charge member 110. In doing so, the radius fillers provide additional structural reinforcement to this joint and distribute the shear and moment forces in order to reduce the risk of delamination at the noodle region of the I-stringer.
However, despite the use of conventional radius fillers, delamination may occur due to localized high shear loads and moments imparted at the web joint. This delamination results in a reduction of joint capability with a possibility of other undesirable effects. One solution may be to provide additional reinforcement at the web joint of the I-stringer. However, adding additional weight to the aircraft is undesirable.
It is with respect to these considerations and others that the disclosure made herein is presented.